Temperature-robust calibration path optical design

A kit comprising at least one spectrometer device for obtaining spectroscopic information on at least one sample and at least one external calibration target, wherein the external calibration target has a reflectance Rλ,ext,

• wherein the spectrometer device comprises
• at least one detector for detecting detection light from a sample;
• at least one optical filter configured for transferring incident light within at least one selected wavelength range onto the detector;
• at least one light source configured for emitting illumination light in at least one optical spectral range;
• at least one sample interface configured for allowing the illumination light to illuminate a sample held by the sample interface and configured for allowing light from the sample held by the sample interface to propagate via the optical filter to the detector;
• at least one first optical path, wherein the first optical path is configured for allowing the illumination light to propagate via the optical filter to the detector by passing the sample interface at least once;
• at least one internal calibration target having a reflectance Rλ,int, and
• at least one second optical path, wherein the second optical path is configured for allowing the illumination light to propagate via the optical filter to the detector by interacting with the internal calibration target at least once;
• wherein spectrometer device is configured for performing at least one initial calibration of the second optical path by using the external calibration target as sample held by the sample interface, and wherein the reflectance Rλ,ext of the external calibration target and the reflectance Rλ,int of the internal calibration target are proportional to each other with
• R
• λ
• ,
• ext
• =
• a
• ·
• R
• λ
• ,
• i
• ⁢
• n
• ⁢
• t
• ,
• wherein α is a constant.